The present invention relates to swivels for connecting fluid flow lines. In particular, the present invention relates to unbalanced swivels for connecting fluid flow lines.
A swivel for rotatably connecting fluid flow lines is typically a multi-component device with least two ends which are connectable to fluid flow lines. In practice, such a swivel includes a male component and a female component. The male and female components often have male and female portions, respectively, such that the male port,on fits within the female portion. Both the male and female components have one or more flow line connectors for connecting the male and female components to fluid flow lines.
The swivel must also have a mechanism for retaining the male portion within the female portion and a mechanism for reducing frictional forces between the male and female components such that the male and female components are rotatable relative to each other. It is known in the art to include bearing race portions in facing annular surfaces of the male and female portions such that a ball bearing is positionable between the male and female portions. The ball bearing thereby retains the male portion inside the female portion and also allows relative rotational movement of the male and female components.
A swivel for rotatably connecting fluid flow lines in which a flowing fluid places greater forces upon the downstream swivel components than upon the upstream swivel components is an example of an unbalanced fluid flow line connection swivel. Positioning of the ball bearing within a bearing race of the male and female components prevents the male and female components from separating due to the unbalanced fluid forces. However, it is known in the art that the unbalanced fluid forces accelerate ball bearing race wear, as compared to that of a swivel having balanced fluid forces.
One approach to solving the bearing race wear problem of unbalanced swivels has been to harden the male and female components. Hardened metal is more resistant to penetration and therefore undergoes less wear from imposed ball bearing loads than does unhardened metal. Another attempted solution to the unbalanced swivel bearing race wear problem entails hardening the male and female portions only, rather than the entirety of the male and female components.